This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 198 44 035.9, filed on Sep. 25, 1998, the entire disclosure of which is incorporated herein by reference.
The invention relates to a shell component for an aircraft fuselage comprising at least one metal skin sheet or panel, a plurality of stringers extending in the aircraft lengthwise direction, and a plurality of frame members extending crosswise relative to the stringers, i.e. in a direction generally circumferentially around the aircraft lengthwise direction. A welding supplemental or filler material is provided on the fuselage skin in the area of the connections between the stringers and the skin, and the stringers are welded onto the fuselage skin in these areas.
In the field of aircraft construction it is presently typical to use riveting or adhesive bonding for joining the fuselage skin panels onto the stringers to fabricate respective fuselage shell components. The assembly and connection of the frames is carried out in a subsequent fabrication step, for which angled mounting elements, particularly so-called clips, are riveted onto the stringers. The clips then serve to connect the frames onto the stringers. In view of such a multistep process, the present conventional fabrication of structural components such as fuselage shell components comprising plural skin-stringer-frame connections entails a rather high expense and effort with respect to the materials and the assembly work that is required. Moreover, the resulting structure has a relatively high weight.
It is a constant and important goal in the development of new aircraft structures to achieve a weight reduction and a cost reduction in the finished aircraft fuselage component. For these reasons, it is necessary to depart from the traditional joining methods using riveting, adhesive bonding, and mechanical mounting clips, and instead to develop an improved joining method that can realize the desired weight reduction and cost reduction.
German Patent 196 39 667 and corresponding U.S. Pat. No. 5,841,098 (Gedrat et al.) disclose a method for welding profiles or sectional members onto large-format aluminum structural components using laser beams to carry out the welding. Such aluminum structural components that are assembled in a skin-stringer manner can be used for the manufacture of an aircraft fuselage. However, there is still room for improvement in the particular structural arrangement and method of assembling the various parts, and especially the crosswise frames and lengthwise stringers, to achieve a simplified, lighter, and more economical aircraft fuselage structure.
In view of the above, it is an object of the invention to provide an improved shell component for an aircraft fuselage comprising frames, stringers, and skin panels, which can be simply and directly joined together by means of welding. It is also an object of the invention to provide an improved fabrication process using welding to join together the several parts of the shell component. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved according to the invention in a shell component for an aircraft fuselage comprising at least one skin panel (e.g. of metal), a plurality of stringers extending in the lengthwise direction of the aircraft, and a plurality of frames extending crosswise or circumferentially relative to the aircraft lengthwise direction, i.e. crosswise relative to the stringers. The skin panel is provided with a welding supplement or filler material in the area of each joint between the skin panel and the stringers, and the stringers are welded to the skin panel at these areas.
Particularly, according to a first embodiment of the invention, a welding supplement or filler material is additionally provided on the skin panel in the area of each joint between the skin panel and the frames, which are also welded to the skin panel. The frames each respectively comprise a frame root portion and a frame profile portion that are ultimately connected to each other. The frame root portion has notches or cut-outs therein and the stringers extend through these notches. A welded connection is provided between the skin panel and each frame root at locations between the respective notches.
According to a second embodiment of the invention, a welding supplement or filler material is also provided on the skin panel in the area of each connection between the skin panel and the frames. In this embodiment, the stringers are respectively embodied as stringer webs. A stringer-frame grid made up of stringer flanges and frame flanges is provided, wherein the stringer flanges are connected to the stringer webs by respective weld joints. The frames are respectively formed of a one-piece or unitary frame element which essentially comprises a frame web and a root portion provided with cut-outs or notches. The frame element is arranged with the root portion in contact on the skin panel and with the frame web lying on the face of the frame flange. The root portion of each frame element is welded to the skin panel.
According to a third embodiment of the invention, a welding supplement or filler material is also provided on the skin panel in the area of each connection between the skin panel and the frames. The stringers are respectively embodied as stringer webs, while the frames respectively comprise a frame web and a frame head. The stringer webs and the frame webs are welded onto the skin panel in the area of the grid pattern provided with the welding filler material. A stringer-frame grid made up of stringer flanges and frame flanges is provided, whereby the stringer flanges are welded to the stringer webs and the frame flanges are welded to the frame webs, by means of respective weld joints. Each respective frame head is arranged and joined onto the respective frame flange by means of another weld joint.
The above objects have further been achieved by methods according to the invention for fabricating a shell component for an aircraft fuselage. A method of fabricating the shell component according to the first embodiment involves the following steps: a welding filler material is applied to the skin panel at the areas of the joints between the skin panels and the stringers as well as the frames; the stringer webs are welded onto the skin panel; each frame root portion is welded onto the stringer-strengthened skin panel; and each frame profile portion is welded onto the frame root portion.
A method of fabricating the shell component according to the second embodiment of the invention comprises the following steps: a welding filler material is applied onto the skin panel at the connection locations between the skin panel and the stringer webs as well as the frame elements; the stringer webs are welded onto the skin panel; the stringer flanges of the stringer-frame grid are welded onto the stringer webs by means of I-joints; the root portions of the frame elements are joined onto the skin panel by welded joints, preferably formed as double fillet joints; and the frame webs of the frame elements are joined onto the faces of the frame flanges by means of welded joints, preferably formed as single-bevel butt weld joints.
A method of fabricating the shell component according to the third embodiment of the invention comprises the following steps: a welding filler material is applied to the skin panel at the connection locations between the skin panel and the stringer webs as well as the frame elements; the stringer webs and the frame webs are welded onto the skin panel in the area of the welding filler material, whereby the stringer webs and the frame webs form a web grid; the stringer flanges and the frame flanges of the stringer-frame grid are welded onto the stringer webs and the frame webs respectively by means of I-joints; and the frame heads are welded onto the respective frame flanges by means of welded joints, preferably double fillet joints.